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Inocybe unicolor

[Basidiomycota > Agaricales > Inocybaceae > Inocybe . . . ]

by Michael Kuo

Inocybe unicolor is a small to medium-ish mushroom that features a scaly stem and a slightly fibrillose brown cap that usually becomes finely scaly as it matures. The gills are pale, dull yellow before they turn brown with maturity, whereupon the densely packed cheilocystidia cause the pale edges to contrast with the faces. The flesh in the very base of the stem is white—which helps to separate it from several similar species that have yellow flesh in the stem base. Under the microscope, Inocybe unicolor has smooth, bean-shaped spores and distinctive, long cheilocystidia.

Inocybe unicolor has often gone under the name of "Inocybe caesariata," but Inocybe expert Brandon Matheny (Matheny & Horman, 2013) tells us that Inocybe caesariata is a poorly known, strictly European species, and that North American mycologist Charles Peck gave the name Inocybe unicolor to our continent's similar species in 1898.


Ecology: Mycorrhizal; growing alone, scattered, or gregariously under oaks and other hardwoods, especially in grassy, urban areas; late spring through fall; possibly widely distributed in eastern North America. The illustrated and described collections are from Illinois.

Cap: 2–5 cm; at first convex, expanding to planoconvex or nearly flat; dry; fibrillose, becoming finely scaly; dull orangish brown.

Gills: Narrowly attached to the stem; close; short-gills frequent; very pale, dull yellow when young, becoming yellowish brown; edges by maturity becoming whitish and contrasting with the faces.

Stem: 3–5 cm long; 3–5 mm thick; more or less equal above a slightly tapered base; dry; fibrillose-scaly over the lower portion or nearly overall; brownish; basal mycelium white.

Flesh: Whitish; unchanging when sliced.

Odor: Weakly to strongly foul and reminiscent of coal tar.

Chemical Reactions: KOH gray on cap surface.

Spore Print: Medium brown.

Microscopic Features: Spores 8–11.5 x 4–6 µm; ellipsoid or bean-shaped; smooth; walls 0.5–1 µm thick; yellowish to brownish golden in KOH; walls brownish in Melzer's reagent. Basidia 4-sterigmate; becoming yellowish to golden and collapsing after sporulation. Cheilocystidia 40–75 x 2.5–12 µm; cylindric and flexuous with rounded, subclavate, or subcapitate apices; occasionally slightly ventricose; occasionally septate and clamped at septa; thin-walled; smooth; hyaline in KOH. Pleurocystidia not found. Pileipellis a collapsing trichoderm; elements brown-walled in KOH, smooth, 2.5–7.5 µm wide, clamped.

REFERENCES: Peck, 1898. (Saccardo, 1899; Kauffman, 1924 [caesariata]; Phillips, 1991/2005 [caesariata]; Lincoff, 1992 [caesariata]; Matheny & Horman, 2013; Matheny, 2017.) Herb. Kuo 08281401, 06181501.

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Inocybe unicolor

Inocybe unicolor

Inocybe unicolor

Inocybe unicolor

Inocybe unicolor

Inocybe unicolor
Spore print

Inocybe unicolor

Inocybe unicolor

Inocybe unicolor

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Kuo, M. (2017, December). Inocybe unicolor. Retrieved from the MushroomExpert.Com Web site: